Tooth decay (caries) is caused by the decomposition, due to bacterial action, of sugars left by liquid or solid foodstuffs in the oral cavity in general and on the teeth in particular. This decomposition produces acids that are liable to attack and eventually dissolve the tooth enamel, resulting in tooth decay.
The modern attitude with respect to tooth decay is to take preventive measures at the earliest possible stage, that is, with the appearance of the first milk teeth of an infant, by removing from the oral cavity all traces of the sugars in their various forms contained in practically all liquid nutrients. Bottle-fed babies and toddlers cannot, however, be expected to rinse their mouths after drinking their bottles of milk, fruit Juice, etc., and must have their mouths cleansed for them.